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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
-"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
-<!ENTITY % entities SYSTEM "custom-entities.ent" >
-%entities;
-]>
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
+ SPDX-License-Identifier: LGPL-2.1+
+
This file is part of systemd.
Copyright 2014 Zbigniew Jędrzejewski-Szmek
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
-<refentry id="sd_event_add_defer" conditional="ENABLE_KDBUS">
+<refentry id="sd_event_add_defer" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_event_add_defer</title>
<refname>sd_event_add_defer</refname>
<refname>sd_event_add_post</refname>
<refname>sd_event_add_exit</refname>
+ <refname>sd_event_handler_t</refname>
<refpurpose>Add static event sources to an event loop</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
+ <funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
+
+ <funcsynopsisinfo><token>typedef</token> struct sd_event_source sd_event_source;</funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef>
+ <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
+ <paramdef>void *<parameter>userdata</parameter></paramdef>
+ </funcprototype>
<funcprototype>
<funcdef>int <function>sd_event_add_defer</function></funcdef>
<paramdef>void *<parameter>userdata</parameter></paramdef>
</funcprototype>
- <funcprototype>
- <funcdef>typedef int (*<function>sd_event_handler_t</function>)</funcdef>
- <paramdef>sd_event_source *<parameter>s</parameter></paramdef>
- <paramdef>void *<parameter>userdata</parameter></paramdef>
- </funcprototype>
-
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
- <para>Those three functions add new event sources to an event loop
- object. The event loop is specified in
- <parameter>event</parameter>, the event source is returned in the
- <parameter>source</parameter> parameter. The event sources are
- enabled statically and will "fire" when the event loop is run and
- the conditions described below are met. The handler function will
- be passed the <parameter>userdata</parameter> pointer, which may
- be chosen freely by the caller.</para>
+ <para>These three functions add new static event sources to an
+ event loop. The event loop object is specified in the
+ <parameter>event</parameter> parameter, the event source object is
+ returned in the <parameter>source</parameter> parameter. The event
+ sources are enabled statically and will "fire" when the event loop
+ is run and the conditions described below are met. The handler
+ function will be passed the <parameter>userdata</parameter>
+ pointer, which may be chosen freely by the caller.</para>
<para><function>sd_event_add_defer()</function> adds a new event
- source that will "fire" the next time the event loop is run. By
- default, the handler will be called once
- (<constant>SD_EVENT_ONESHOT</constant>).</para>
+ source that will be dispatched instantly, before the event loop
+ goes to sleep again and waits for new events. By default, the
+ handler will be called once
+ (<constant>SD_EVENT_ONESHOT</constant>). Note that if the event
+ source is set to <constant>SD_EVENT_ON</constant> the event loop
+ will never go to sleep again, but continuously call the handler,
+ possibly interleaved with other event sources.</para>
<para><function>sd_event_add_post()</function> adds a new event
- source that will "fire" if any event handlers are invoked whenever
- the event loop is run. By default, the source is enabled
- permanently (<constant>SD_EVENT_ON</constant>).</para>
+ source that is run before the event loop will sleep and wait
+ for new events, but only after at least one other non-post event
+ source was dispatched. By default, the source is enabled
+ permanently (<constant>SD_EVENT_ON</constant>). Note that this
+ event source type will still allow the event loop to go to sleep
+ again, even if set to <constant>SD_EVENT_ON</constant>, as long as
+ no other event source is ever triggered.</para>
<para><function>sd_event_add_exit()</function> adds a new event
- source that will "fire" when the event loop is terminated
- with <function>sd_event_exit()</function>.</para>
+ source that will be dispatched when the event loop is terminated
+ with <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
<para>The
<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
function may be used to enable the event source permanently
(<constant>SD_EVENT_ON</constant>) or to make it fire just once
- (<constant>SD_EVENT_ONESHOT</constant>). If the handler function
- returns a negative error code, it will be disabled after the
- invocation, even if <constant>SD_EVENT_ON</constant> mode is
- set.</para>
+ (<constant>SD_EVENT_ONESHOT</constant>).</para>
+
+ <para>If the handler function returns a negative error code, it
+ will be disabled after the invocation, even if the
+ <constant>SD_EVENT_ON</constant> mode was requested before.</para>
+
+ <para>To destroy an event source object use
+ <citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ but note that the event source is only removed from the event loop
+ when all references to the event source are dropped. To make sure
+ an event source does not fire anymore, even when there's still a
+ reference to it kept, consider setting the event source to
+ <constant>SD_EVENT_OFF</constant> with
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
+
+ <para>If the second parameter of these functions is passed as
+ NULL no reference to the event source object is returned. In this
+ case the event source is considered "floating", and will be
+ destroyed implicitly when the event loop itself is
+ destroyed.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
- <para>On success, this functions return 0 or a positive
+ <para>On success, these functions return 0 or a positive
integer. On failure, they return a negative errno-style error
code.</para>
</refsect1>
</variablelist>
</refsect1>
- <refsect1>
- <title>Notes</title>
-
- <para>Functions described here are available as a shared library,
- which can be compiled and linked to with the
- <constant>libsystemd</constant> <citerefentry
- project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
- file.</para>
- </refsect1>
+ <xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>See Also</title>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_now</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_priority</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_source_set_description</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_event_exit</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
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